$(document).ready(function() { 


 $("#firstBox, #secondBox, #thirdBox, #forthBox").bind("change keyup blur",function cal () { 
 $("#thirdBox").val(Math.ceil(((Number($("#forthBox").val()) * Number ($ ("#secondBox").val()) )/100 )-  Number($("#firstBox").val()))); 

}); 

$("#Increase").click(function() { $("#forthBox").val(5 + Number($("#forthBox").val()) );  $("#thirdBox").val(Math.ceil(((Number($("#forthBox").val()) * Number 
($ ("#secondBox").val()) )/100 )-  Number($("#firstBox").val()))); 
}); 


$("#Decrease").click(function() {   $("#forthBox").val( Number($("#forthBox").val()) - 5 );  $("#thirdBox").val(Math.ceil(((Number($("#forthBox").val()) * Number 
($ ("#secondBox").val()) )/100 )-  Number($("#firstBox").val()))); 
}); 

$("#firstBox").numeric();
$("#secondBox").numeric(); 
$("#thirdBox").numeric(); 
$("#forthBox").numeric(); 
$("input:visible:enabled:first").focus();

});